Seoul, South Korea — Park Geun-hye won a decisive victory Wednesday after a bitterly fought election for president of South Korea in which she overcame criticism of her legacy as the daughter of long-ruling dictator Park Chung-hee. In so doing, she also overcame traditional barriers to women in government and business to become the first woman to win her country's presidency.

With nearly all votes counted, and a commanding 3.6 percentage point lead over liberal candidate Moon Jae-in, Ms. Park entered her party headquarters to loud cheers from conservative party leaders and thanked them for all their "effort and time" – and for turning out in freezing temperatures. Next, she climbed into her limousine and headed to central Seoul, where thousands cheered her for winning an election that many analysts said would end in a virtual dead heat.

Under the glare of huge spotlights in front of the palace of bygone Korean kings, Park vowed to be a “president of the people” and to keep her promise to reinvigorate a stagnating economy and fight for reunification with North Korea.

Far from eking out a marginal victory, Park maintained an unexpectedly high lead as returns poured in from ballots cast by more than 25 million people. Nearly 80 percent of eligible voters went to the polls – more than expected – in what many saw as a test of support for conservative economic policies and a firm stance against North Korea.

“She’s the right person [to] overcome these difficulties,” says Hwang Jin-ha, a retired Army general and member of the National Assembly from the conservative Saenuri, or New Frontier Party, headed by Park. That remark reflects concerns not only about the economy, but also about North Korea in the aftermath of the launching a week ago of a rocket that put a satellite into orbit.

“She would talk with North Korea but with conditions," says Mr. Hwang, meaning that she would demand the North get rid of its missile and nuclear program.

Park will succeed conservative President Lee Myung-bak, a former Hyundai Construction executive, when he steps down in February. Her triumph returns her to the Blue House, the center of presidential power, where she was her country's first lady after the assassination of her mother in 1974 by a bullet intended for her father. He in turn was assassinated by his intelligence chief in 1979.

She’s distanced herself from Mr. Lee's party in view of his growing unpopularity, including corruption scandals that landed one of his brothers in jail. Still, she's expected to perpetuate his conservative policies with new emphasis on the welfare of the middle class and small and medium enterprise.

The role of older voters

At Mr. Moon's headquarters, disconsolate aides, waiting for him to concede defeat, attributed his loss to the tendency of older voters to vote conservative.

“It’s all the people in their 50s and 60s,” says Shin Ji-yong, on Moon's campaign staff. “That’s the reason."

Middle-aged and elderly voters tended to favor Park partly because of their memories of the economic achievements of her father, despite his record as a dictator. Many also were concerned about Moon's stance on North Korea, which is considerably softer than Park's.

As leader of the Democratic United Party and former top aide to the liberal Roh Moo-hyun, president from 2003 to 2008, Moon hoped to revive the Sunshine policy of reconciliation pursued for 10 years by Mr. Roh and his predecessor, Kim Dae-jung. The fear among conservatives was that he would make concessions to North Korea while failing to demand the North give up its nuclear and missile programs.

In fact, older voters who might have stayed home cast their ballots in order to head off Moon’s appeal to a broad spectrum of younger voters. Notorious for ignoring elections, young voters also turned out in greater numbers than usual – though not enough to overcome the voting power of the their elders.

Moon became popular among young people after he consolidated his campaign by persuading the popular software entrepreneur, Ahn Cheol-soo, to drop out of the race and support him. It was that early political deal that convinced many observers, including a number of pollsters, that he had a serious chance of pulling off an upset.

Moon appeared at midnight saying he was “sorry for disappointing” his supporters and politely applauding aides for their loyalty.

“I admit my campaign was a failure,” he said, “but it’s not the failure of the desire of the Korean people to open a new era” – a remark that suggests the depth of opposition that Park will face after her inauguration in February.